top of page


Can cancer be caused by an infection?

Since the start of the 20th century, it’s been known that certain infections play a role in cancer in animals. More recently, infections with certain viruses, bacteria, and parasites have been recognized as risk factors for several types of cancer in humans.

Worldwide, infections are linked to about 15% to 20% of cancers. This percentage is even higher in developing countries, but it is lower in the United States and other developed countries. This is partly because certain infections are more common in developing countries, and partly because some other risk factors for cancer, such as obesity, are more common in developed countries.

Infections can raise a person’s risk of cancer in different ways. For example:

  • Some viruses directly affect the genes inside cells that control their growth. These viruses can insert their own genes into the cell, causing the cell to grow out of control.

  • Some infections can cause long-term inflammation in a part of the body. This can lead to changes in the affected cells and in nearby immune cells, which can eventually lead to cancer.

  • Some types of infections can suppress a person’s immune system, which normally helps protect the body from some cancers.

Any of these changes might lead to a higher risk of cancer.

Even though the infections described here can raise a person’s risk of certain types of cancer, most people with these infections never develop cancer. The risk of developing cancer is also influenced by other factors. For example, infection with Helicobacter pylori (H pylori) bacteria might increase your risk of stomach cancer, but what you eat, whether or not you smoke, and other factors also affect your risk.

Many of the infections that influence cancer risk can be passed from person to person, but cancer itself cannot. A healthy person can’t “catch” cancer from someone who has it.

Know your risk of infection

It’s important to weigh the risk of infection and other side effects against the benefits of cancer treatment. Talk with your doctors before or during chemotherapy or radiation therapy to see how this information applies to you.


Here are some questions you can ask your doctor or cancer care team before and during cancer treatment:

  • Will this cancer treatment make me more likely to get infections?

  • Will you do anything special to help keep me from getting infections during treatment?

  • What can I do to lower my risk of infection?

  • How will I know if I have an infection?

  • What kinds of infections are most common for someone in my situation?

  • What should I do if I think I have an infection?

  • If I get a fever, does that mean I have an infection?

  • How will you decide how to treat my infection?

  • What will you do if the treatment doesn’t get rid of my infection?

  • What are the likely side effects of the treatments for infection?

What are signs of infection in people with cancer?

What are signs of infection in people with cancer?

It’s important to watch for early signs of infection and tell your health care team about them right away. This way treatment can be started as early as possible. This is most important for people who have a low white blood cell count. This is discussed in How does your body normally resist infections?

Signs and symptoms of an infection might include:

  • Body temperature of 100.5º F or higher (a fever) taken by mouth

  • Shaking chills or sweats (often goes along with fever)

  • Sore throat

  • Sores or white coating on your tongue or in your mouth

  • Cough or shortness of breath

  • Nasal congestion

  • Burning or pain when urinating; bloody or cloudy urine

  • Redness, swelling, drainage, or warmth at the site of an injury, surgical wound, or vascular access device (VAD), or anywhere on the skin including the genital and rectal areas

  • Pain or tenderness in the stomach or abdomen (the belly)

  • Stiff neck

  • Sinus pain, ear pain, or headache

  • Swelling or redness anywhere

Fever is especially important because it’s often the first sign of an infection in people with cancer. You should have a thermometer to check your temperature – you can’t rely on how you feel to know when you have a fever. Patients may be told to call their doctor or nurse if they have a temperature of 100.5º F or higher, or if they have other signs and symptoms of infection. Don’t take medicines to reduce your fever (such as Tylenol®, Advil®, Motrin®, or aspirin) without checking with your doctor first. Ask your doctor what you should do and when you should call. Be sure you know how to reach your health care team after hours, including nights and weekends.

Key things you need to know

It’s important for people with cancer and their families and friends to know these things:

  • Your risk for infection

  • How long your immune system is likely weak after treatment

  • How to take your temperature the right way, when to check it, and how often to check it

  • When to report fever or other signs and symptoms of infection to the doctor or nurse

  • The importance of handwashing and hygiene for the patient and the people they come in contact with

  • How to take good care of your mouth and check for sores and signs of infection

  • How to clean cuts, scrapes, or other breaks in the skin and keep them clean to help prevent infection

  • The importance of cleaning around the anus after each bowel movement, using moist towelettes or baby wipes

  • Good care of IVs and central venous catheters (CVCs, like ports and PICC lines)

  • Where to look for signs of infection (skin, mouth, and CVC sites)

  • The importance of good nutrition, a balanced diet, and drinking plenty of fluids

  • The importance of sleep and exercise

  • The need to take medicines as prescribed

  • Being sure the doctor knows about all medicines you’re taking (prescription, over-the-counter, vitamins, herbs, and supplements) – keep a list and update it at each doctor visit

  • Ways to prevent dryness of the skin and mucous membranes

  • You need to talk with your health care team or doctor before getting vaccinated (immunized) and before getting close to children or adults who have recently had vaccinations. (See Vaccination During Cancer Treatment for more on this.)

Review these points with your doctor or nurse before and during treatment to get the information you need. Double-check with them on how you should handle these things and find out if there are any special steps you should take during cancer treatment.



Consult a doctor for medical advice or visit us at PEOPLE CARE INSTITUTE for more information


Note: The information you see here is general and describes what usually happens with a medical condition, but doesn't apply to everyone. This information IS NOT  a substitute for professional medical advice, so please make sure to contact a healthcare provider if you have a medical problem. 

bottom of page